USAG Angled Open-Socket Wrench (291 series....same as Facom 76 series) - deep recess at one end and open end socket at the other fit over protruding studs (6-point on one end, 12pt on the other). The angle and through hole design accommodates threadedrods or a bar for extra leverage without affecting wrench strength. This is one of my favorite USAG/Facom products for field installations (cabinets, shelving, garage door track, etc).